Effective HIV preventive interventions have been developed and evaluated with adolescents. This research team has designed, mounted and evaluated HIV prevention programs with 4 adolescent samples at high risk for HIV: runaway youth (n=312), gay youth (n=154), Youth Living with HIV (n=351), and Youth with Parents with AIDS (n=423 adolescents from 280 different families). Each of these samples reflects a sub-population at high risk of contracting or transmitting HIV; each is composed predominantly for African-American and Latino youth aged 12-20 years. For each population, an intervention was designed based on social learning theory that focused primarily on skill building and aimed at reducing sexual and substance use risk acts; each intervention also was tailored for the specific population. Each intervention was delivered in a small group setting, used tokens to encourage social rewards, and monitored affect by the use of a Feeling Thermometer. Homework assignments were common across interventions and multiple sessions were implemented. Each sample has been followed for at least 2 years; the assessment points for follow-up were at least 3, 6, 12, 18, and 24 months. The measures were designed by the same research team and the domains of assessment were similar. Each sample was assessed for sex and drug use While the field of HIV prevention has demonstrated that adolescents do reduce their sexual and substance use risk acts in response to intervention programs, there have been no evaluations of the cost effectiveness of these programs. This project will evaluate the cost-effectiveness of each of the 4 adolescent prevention programs already mounted and compare the consistency of the cost-effectiveness findings across studies. The project will proceed in 3 phases. First, building on a cost- effectiveness analysis of the HIV intervention on runaway youth, this project will use the existing data to perform the cost- effectiveness analysis of the other 3 HIV intervention programs which were delivered to adolescents (youth living with HIV, gay youth, and youth whose parents living with AIDS). Second, the results of these 4 cost-effectiveness analyses will be used to examine the similarity and the consistency of the cost- effectiveness of different HIV-related intervention programs. Third, because HIV sex risk acts among adolescents are usually part of a cluster of problem behaviors, this project will expand current strategies for examining cost-effectiveness to include social outcomes such as foster care, mental health institutionalization, jail and temporary shelter.